1. Field of the Invention
The invention relates to local area networks (LANs) and more particularly, to connecting two twisted pair lines.
2. Prior Art
Local area networks (LANs) have become widely used, particularly to interconnect personal computers, servers, peripherals, etc. Among the most popular LANs is Ethernet which often uses a 50 ohm coaxial cable or uses an unshielded twisted pair line having 100 ohm characteristic impedance.
In these networks with unshielded cables, it is often desirable that the current in the medium be balanced, that is, that the network operate in a differential mode since this prevents troublesome radiation and limits susceptibility to external electronic noise. There are numerous well-known circuits, filters, terminators, etc. for preventing radiation from and limiting the susceptibility of these networks.
As will be seen, the present invention provides for common mode current cancellation where two twisted pair lines are connected together.